**5. Conclusions and Future Prospects**

By analyzing the internal relationship between ecological civilization, beautiful China, and PLES, as well as the scientific connotations of PLES, this paper systematically organized the optimization theory, methods, and practices for PLES around territorial spatial planning, with the overall planning of PLES as the goal, and the promotion of ecological civilization construction as the starting point. We also proposed an optimization approach for PLES. Based on the analysis and summary, the main research directions for the overall optimization of PLES in the future should include the following:

(1) Research on the main regional types and differentiation rules of PLES: This paper studied the distribution characteristics of the functional spatial patterns of PLES at multiple scales. In this way, the scale differences and functional complexities of PLES under different spatial scales were clarified. Moreover, classification and identification systems for PLES under different scales and different regional types were established.

(2) Analysis and research on the evolution process, structural characteristics, and development trends of PLES: The dynamic spatial and temporal evolution characteristics of the structural proportion and spatial scale of PLES were analyzed, including regional suitability and carrying capacity evaluation, regional differences in space, and development over time. Moreover, the coupling coordination degree and conflict mechanism in the evolutionary process of PLES were revealed.

(3) Analysis of the internal nonlinear mechanism for the PLES System: Guided by the theory of the human–Earth system, we revealed the competition and synergistic interactions and positive feedback mechanisms between population, resources, ecology, environment, and economic and social development in the PLES system, and identified the nonlinear dynamic effects among subsystems and elements in the system.

(4) Analysis of the mechanism for matter and energy transfer in the overall optimization system of PLES: Based on the regional resource metabolism theory and the geographical patterns of PLES, we deeply analyzed the transfer path, flow process, and metabolic mechanisms of key elements, such as water, soil, energy, and carbon, in the co-evolution process of PLES.

(5) Development and application of a simulation model and multi-objective optimization model for the overall optimization system of PLES: Studies should make full use of the research results for the nonlinear dynamic mechanisms, transmission paths, and flow processes of key elements in the PLES system, and carry out research on overall optimization strategies and scenario predictions for PLES in different regions, at different scales, and for different types.

(6) Research, development, and application of the overall optimization and decision support platform for PLES: A visual support platform was developed with integrated functions for data processing, spatio-temporal analysis, scenario simulation, result output, problem diagnosis, and early warning and control. This platform can help coordinate the government at all levels, and between different departments and different areas of the target demand, to facilitate population migration, urban and rural construction and industrial development, resource development, ecological construction, environmental protection, infrastructure construction, public services and disaster prevention, and mitigation-system spatial deployment as components of unified and consensus development goals and plans.

**Author Contributions:** G.L. and J.F. contributed to all aspects of this work; D.J. conducted data analysis; and G.L. and Y.Z. wrote the main manuscript text. All authors reviewed the manuscript. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by grants from the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA19040305), Youth Innovation Promotion Association (Grant No. 2018068), and Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences (Grant No. E0V00112YZ).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available on request from the author.

**Conflicts of Interest:** The authors declare no conflict of interest.
